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I'm having a problem with kernel using much cpu on latest ubuntu 21.10.

one core is used at 80%

the kworker uses actually 10% of CPU which is 80% on one core

I've tried to do this workaround: https://www.linuxquestions.org/questions/linux-software-2/high-cpu-usage-by-kworker-4175563563/ but matter what I did, I can't modify the dirty_writeback_centisecs file. Sometimes after some "Main components update" or GPU driver update problem goes away, but then it returns, and I have no idea what to do.

dronostyka
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  • A bug as old as the street, not frequently reported because many users find it normal that the fan is on all the time. The accepted answer in the thread I referred to helped me. It is rather complicated, though: you have to identify and disable interrupts that cause the problem. For me, it was enough to disable gpe13. I have this in effect since 2019 - would need to test if it is still needed in Ubuntu 21.10. – vanadium Dec 17 '21 at 12:02
  • So I've just tried these solutuions: https://askubuntu.com/questions/176565/why-does-kworker-cpu-usage-get-so-high but it says no permision when i try to disable interrurpt which has high number I get permision denied. – dronostyka Dec 17 '21 at 12:11
  • How did you disable them? Because for me even using sudo won't let it disable. I'm wondering if disabling whole ACPI would help.. – dronostyka Dec 17 '21 at 12:13
  • I just followed the instructions. I live with a line in my crontab, and with a /etc/pm/sleep.d/30_disable_gpe6F file that executes the same command after sleep or hibernate. Still from 19.10: against better advise, I have been upgrading since then rather than installing anew. – vanadium Dec 17 '21 at 12:16
  • Seems like it says no permission, but now CPU usage loks good. – dronostyka Dec 17 '21 at 12:21
  • I cannot see where it could say that, but anyway, keep a watch. If not solved, the problem will reappear any time sooner or later after rebooting. – vanadium Dec 17 '21 at 13:31
  • Yes you were right, usage seems to go away while working on battery. I had to reinstall ubuntu yesterday and now it's ok. – dronostyka Dec 18 '21 at 19:01
  • I have also noticed that reconnecting external display removes the problem for some time. – dronostyka Dec 31 '21 at 11:57

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